Pure ammonia internal combustion engine and control method thereof

Abstract

The invention relates to the field of internal combustion engines and provides a pure ammonia internal combustion engine and a control method thereof. The pure ammonia internal combustion engine comprises a cylinder. A piston configured to reciprocate within the cylinder; the combustion chamber is defined by the air cylinder and the piston, and the combustion chamber is a spherical combustion chamber with a squeezing port; the composite ignition system comprises a spark plug, a glow plug and a control unit, and the control unit is configured to adopt at least one of spark plug ignition, glow plug ignition and jet flow ignition based on the operation working condition of the engine. The pure ammonia internal combustion engine can provide a flexible mixed gas forming mode, the stability of ammonia combustion is effectively improved, a solution is provided for solving the existing problems that ammonia ignition is difficult, the flame propagation speed is low, the unburned ammonia emission level is high and the like, and application of ammonia fuel in the field of internal combustion engines is assisted.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engines, and provides a pure ammonia internal combustion engine and its control method. Background Technology

[0002] In the context of the current energy structure transformation, ammonia is receiving widespread attention as a potential zero-carbon fuel. When ammonia is completely burned, it produces only nitrogen and water, with no carbon dioxide emissions, thus being considered an ideal choice for promoting a green energy transition. Ammonia production processes are mature, and its storage and transportation technologies are relatively well-developed, demonstrating enormous application potential.

[0003] In practical applications, ammonia fuel faces numerous challenges. Firstly, ammonia has a high auto-ignition point, a large minimum ignition energy, and a narrow combustible range, making its combustion in internal combustion engines difficult to control. This manifests as slow flame propagation and incomplete combustion, which not only affect engine efficiency but also result in high emissions of unburned ammonia. Particularly under low-load conditions, the lower combustion temperature causes ammonia oxidation to tend to follow a cryogenic path, leading to a sharp increase in nitrogen oxide emissions.

[0004] To address these issues, existing technologies often employ blending with other fuels, leveraging the high reactivity of these fuels to improve the ignition stability of ammonia. However, this approach requires additional hydrogen storage cylinders, fuel tanks, or catalytic reforming equipment, significantly increasing system complexity and cost. Summary of the Invention

[0005] This invention provides a pure ammonia internal combustion engine to solve the problems of difficult ammonia ignition, slow flame propagation speed, and high levels of unburned ammonia emissions in related technologies.

[0006] This invention also provides a control method for a pure ammonia internal combustion engine.

[0007] A first aspect of the present invention provides a pure ammonia internal combustion engine, comprising: cylinder; A piston configured to reciprocate within the cylinder; The combustion chamber, defined by the cylinder and the piston, is a spherical combustion chamber with an extrusion port; A composite ignition system includes a spark plug, a glow plug, and a control unit, wherein the control unit is configured to employ at least one of the following methods based on the engine's operating conditions: spark plug ignition, glow plug ignition, and jet ignition.

[0008] According to one embodiment of the present invention, the compression ratio of the pure ammonia internal combustion engine ranges from 20 to 25, the boost ratio ranges from 2 to 4, the ignition energy ranges from 100 to 300 mJ, and the overall fuel-air equivalence ratio ranges from 0.4 to 1.0.

[0009] According to one embodiment of the present invention, a fuel supply system is further included, the fuel supply system comprising an ammonia injector, the fuel supply system supplying ammonia fuel to the combustion chamber via at least one of the following: supplying ammonia gas via a continuous flow valve and a plasma generator, supplying ammonia gas via intake manifold injection, and supplying liquid ammonia via in-cylinder direct injection.

[0010] According to one embodiment of the present invention, it further includes an exhaust gas recirculation line for recirculating hot exhaust gas from the exhaust side of the engine to the intake side; the ammonia injector is configured to inject liquid ammonia into the hot exhaust gas in the exhaust gas recirculation line.

[0011] According to one embodiment of the present invention, the inner surface of the combustion chamber is coated with a thermal barrier coating.

[0012] According to one embodiment of the present invention, it further includes an ammonia injector, the central axis of which forms a predetermined angle with the central axis of the glow plug or the central axis of the spark plug.

[0013] According to one embodiment of the present invention, the ammonia injector is configured to form a locally rich mixture region around the glow plug by controlling at least one of the ammonia injection timing, the injection orifice position, and the injection angle. And / or, The ammonia injector is configured to inject ammonia fuel onto the high-temperature surface of the glow plug.

[0014] A second aspect of the present invention provides a control method for a pure ammonia internal combustion engine as described above, comprising: In the first injection step, during the intake stroke, a first portion of ammonia fuel is injected into the combustion chamber to form a homogeneous mixture; In the second injection step, during the compression stroke, a second portion of ammonia fuel is injected into the combustion chamber to form a stratified mixture; The ignition step employs at least one of the following: spark plug ignition, glow plug ignition, and jet ignition.

[0015] According to one embodiment of the present invention, the first injection step is performed within a crankshaft angle range of 330 degrees to 210 degrees before the top dead center of the compression, and the air-fuel equivalence ratio of the homogeneous mixture is 0.4 to 0.8.

[0016] According to one embodiment of the present invention, the second injection step is performed within a crankshaft angle range of 60 degrees to 0 degrees before the top dead center of the compression stroke, and combustion with an air-fuel equivalence ratio of 1.0 to 1.2 occurs around the spark plug, with an overall equivalence ratio of 0.4 to 1.0.

[0017] According to the pure ammonia internal combustion engine provided in the first aspect of the present invention, the spatial structure of the combustion chamber allows for a more uniform distribution of the ammonia-air mixture within the combustion chamber, avoiding the problems of excessively rich or lean mixtures in traditional combustion chambers, thus laying the foundation for complete combustion of ammonia fuel. It accelerates the contact speed between ammonia molecules and air molecules, overcoming the slow flame propagation speed of ammonia fuel, promoting rapid flame diffusion within the combustion chamber, reducing unburned ammonia residue, and improving combustion efficiency. Addressing the characteristics of ammonia fuel's high auto-ignition temperature and large minimum ignition energy, the composite ignition system achieves stable ignition under all operating conditions through multi-mode control: during startup, the high-temperature surface of the glow plug provides initial ignition energy for the ammonia fuel, preventing ignition failure at low temperatures; during stable operation, the spark plug works independently, balancing ignition efficiency and energy consumption; under special operating conditions, the two work together to further improve ignition reliability. It does not rely on blending with other highly reactive fuels such as hydrogen or diesel; stable ignition can be achieved using only pure ammonia, simplifying the system structure and reducing equipment costs and maintenance difficulty. No additional fuel storage or catalytic reforming equipment is required; efficient combustion can be achieved using only ammonia fuel, with combustion products consisting solely of nitrogen and water, and no carbon dioxide emissions, meeting the requirements for zero-carbon energy. Furthermore, optimized structural design reduces the generation of nitrogen oxides during ammonia combustion, balancing environmental friendliness and combustion efficiency, providing key technological support for the industrial application of pure ammonia internal combustion engines.

[0018] According to the control method for a pure ammonia internal combustion engine provided in the second aspect of the present invention, the homogeneous mixture formed during the intake stroke ensures that ammonia fuel and air are evenly distributed in the combustion chamber, avoiding incomplete combustion due to excessively rich mixtures or ignition failure due to excessively lean mixtures, thus providing a uniform basis for the subsequent formation of stratified mixtures. The formation of the homogeneous mixture relies on the intake airflow and the combustion chamber structure, eliminating the need for additional stirring components, simplifying the control logic, and simultaneously creating conditions for lean combustion of ammonia fuel, improving engine economy and reducing initial unburned ammonia residue. The stratified mixture formed during the compression stroke solves the problem of difficult ammonia fuel ignition through local concentration optimization. The higher concentration of the mixture in the center of the combustion chamber is more easily ignited by the ignition source, while the peripheral homogeneous mixture ensures complete combustion, breaking the limitation of the narrow combustible range of ammonia fuel. The stratified structure also slows down the rate of temperature rise in the initial stage of combustion, inhibiting the formation of nitrogen oxides, especially improving the high nitrogen oxide emissions caused by the low-temperature reaction path of ammonia fuel under low-load conditions, balancing ignition stability and environmental friendliness. The control unit selectively controls the spark plug and / or glow plug according to operating conditions to achieve stable ignition under all conditions: during startup, the high-temperature surface of the glow plug compensates for the insufficient ignition energy of ammonia fuel in low-temperature environments; during stable operation, the spark plug works alone to reduce energy consumption; under special operating conditions, both work together to improve ignition reliability, eliminating the need to rely on mixing with other highly reactive fuels, achieving stable ignition with only pure ammonia, and maintaining the advantages of zero-carbon combustion. The matching of ignition timing with the stratified mixture further promotes rapid flame propagation, reduces unburned ammonia emissions, improves combustion efficiency, and ensures efficient and stable engine operation under different operating conditions. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic structural diagram of the pure ammonia internal combustion engine provided by the present invention.

[0021] Figure 2 This is a schematic structural diagram of the first fuel supply system provided by the present invention.

[0022] Figure 3 This is a schematic structural diagram of the second fuel supply system provided by the present invention.

[0023] Figure 4 This is a schematic structural diagram of the third fuel supply system provided by the present invention.

[0024] Figure 5This is a schematic structural diagram of the first fuel supply system and its control method provided by the present invention.

[0025] Figure 6 This is a schematic structural diagram of the second fuel supply system and its control method provided by the present invention.

[0026] Figure 7 This is a schematic structural diagram of the third fuel supply system and its control method provided by the present invention.

[0027] Figure 8 This is a schematic structural diagram of the first injection of liquid ammonia into a pure ammonia internal combustion engine provided by the present invention.

[0028] Figure 9 This is a schematic structural diagram of the spark plug ignition system for a pure ammonia internal combustion engine provided by the present invention.

[0029] Figure 10 This is a schematic structural diagram of the second injection of liquid ammonia in a pure ammonia internal combustion engine provided by the present invention.

[0030] Figure 11 This is a schematic structural diagram of the jet ignition of a pure ammonia internal combustion engine provided by the present invention.

[0031] Figure 12 This is a schematic structural diagram of the exhaust gas recirculation pipeline provided by the present invention.

[0032] Figure 13 This is a schematic structural diagram of a turbocharged, non-intercooled pure ammonia internal combustion engine provided by the present invention.

[0033] Figure 14 This is a schematic flowchart of the control method for a pure ammonia internal combustion engine provided by the present invention.

[0034] Figure label: 100. Cylinder; 102. Piston; 104. Combustion chamber; 106. Spark plug; 108. Glow plug; 110. Control unit; 112. Ammonia injector; 114. Continuous flow valve; 116. Intake manifold; 118. Exhaust gas recirculation line; 120. Plasma generator; 122. Exhaust gas recirculation device; 124. Turbine shaft; 126. Turbine impeller; 128. Turbine exhaust outlet; 130. Compressor inlet; 132. Compressor impeller; 134. Engine exhaust side. Detailed Implementation

[0035] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0036] like Figures 1 to 13 As shown, a first aspect of the present invention provides a pure ammonia internal combustion engine, comprising: Cylinder 100; Piston 102 is configured to reciprocate within cylinder 100; Combustion chamber 104 is defined by cylinder 100 and piston 102, and combustion chamber 104 is a spherical combustion chamber 104 with extrusion port; The composite ignition system includes a spark plug 106, a glow plug 108, and a control unit 110. The control unit 110 is configured to use at least one of spark plug 106 ignition, glow plug 108 ignition, and jet ignition based on the engine's operating conditions.

[0037] According to the pure ammonia internal combustion engine provided in the first aspect of the present invention, the spatial structure of the combustion chamber 104 allows for a more uniform distribution of the ammonia fuel-air mixture within the combustion chamber 104, avoiding the problems of excessively rich or lean mixtures in traditional combustion chambers 104, thus laying the foundation for complete combustion of ammonia fuel. It accelerates the contact speed between ammonia molecules and air molecules, overcoming the slow flame propagation speed of ammonia fuel, promoting rapid flame diffusion within the combustion chamber 104, reducing unburned ammonia residue, and improving combustion efficiency. Addressing the characteristics of ammonia fuel's high auto-ignition temperature and large minimum ignition energy, the composite ignition system achieves stable ignition under all operating conditions through multi-mode control: during startup, the high-temperature surface of the glow plug 108 provides initial ignition energy for the ammonia fuel, preventing ignition failure at low temperatures; during stable operation, the spark plug 106 works independently, balancing ignition efficiency and energy consumption; under special operating conditions, the two work together to further improve ignition reliability. It does not rely on blending with other highly reactive fuels such as hydrogen or diesel; stable ignition can be achieved using only pure ammonia, simplifying the system structure and reducing equipment costs and maintenance difficulty. No additional fuel storage or catalytic reforming equipment is required; efficient combustion can be achieved using only ammonia fuel, with combustion products consisting solely of nitrogen and water, and no carbon dioxide emissions, meeting the requirements for zero-carbon energy. Furthermore, optimized structural design reduces the generation of nitrogen oxides during ammonia combustion, balancing environmental friendliness and combustion efficiency, providing key technological support for the industrial application of pure ammonia internal combustion engines.

[0038] Please continue reading Figures 1 to 13 The pure ammonia internal combustion engine provided in the first aspect embodiment of the present invention mainly includes a cylinder 100, a piston 102, and a compound ignition system.

[0039] The cylinder 100 is a cylindrical cavity open at both ends. Its inner wall is precision-machined, resulting in a smooth surface and excellent sealing, providing stable guidance for the movement of the piston 102. The piston 102 is a cylindrical structure adapted to the cylinder 100, with a sealing component on its outer periphery that fits tightly against the inner wall of the cylinder 100. It can reciprocate along the axis of the cylinder 100, realizing the cycle of four strokes: intake, compression, power, and exhaust. The top profile of the piston 102 is arc-shaped to fit the combustion chamber 104, ensuring that it, together with the cylinder 100, defines a complete combustion chamber 104 space, and that it does not interfere with the inner wall of the cylinder 100 or other components of the combustion chamber 104 during reciprocating motion.

[0040] Combustion chamber 104 is formed by the inner wall of cylinder 100 and the top of piston 102, and has an overall spherical structure. The spherical design makes the mixture distribution in the combustion space more uniform and avoids incomplete combustion caused by local dead zones. An annular extrusion port is provided along the circumferential edge of combustion chamber 104. The width and depth of the extrusion port are optimized. At the end of the compression stroke, when piston 102 moves upward, the mixture in combustion chamber 104 is squeezed into the extrusion port area, forming a strong extrusion effect, promoting the disturbance and mixing of the mixture, and breaking the limitation of the narrow combustible range of ammonia fuel. The spherical profile of combustion chamber 104 and the extrusion port work together to provide a structural basis for the uniform mixing and stable combustion of ammonia fuel.

[0041] The composite ignition system is integrated into the cylinder head 100, located in the top area of ​​the combustion chamber 104. The spark plug 106 is a high-energy ignition type, with its electrode extending into the combustion chamber 104 and aligned with the center of the combustion chamber 104 to generate an ignition spark through electrode discharge. The glow plug 108 is a resistance heating type, with its heating end also extending into the combustion chamber 104 and located close to the spark plug 106, generating a high-temperature surface through energization. The control unit 110 is an electronic control module with operating condition recognition and signal output functions, which is electrically connected to the spark plug 106 and glow plug 108 through wires, and also communicates with the engine's operating condition sensors.

[0042] The control unit 110 can selectively control the ignition mode based on the engine's real-time operating conditions (such as starting conditions, low-load conditions, stable operating conditions, and high-load conditions): under starting or low-load conditions, the glow plug 108 is energized to generate high temperature to assist in the ignition of ammonia fuel; under stable operating conditions, the spark plug 106 is controlled to discharge and ignite alone to ensure ignition efficiency; under high-load or special conditions, the spark plug 106 and the glow plug 108 are controlled to work simultaneously, and the stable ignition of ammonia fuel is ensured through the synergistic effect of the spark and the high-temperature surface.

[0043] According to one embodiment of the present invention, the compression ratio of the pure ammonia internal combustion engine ranges from 20 to 25, the boost ratio ranges from 2 to 4, the ignition energy ranges from 100 to 300 mJ, and the overall fuel-air equivalence ratio ranges from 0.4 to 1.0.

[0044] In one embodiment of the present invention, the key operating parameters of the pure ammonia internal combustion engine are set within a specific range to adapt to the combustion characteristics of ammonia fuel.

[0045] The compression ratio is set to a higher range, which is achieved by optimizing the top profile of the piston 102 and the volume of the combustion chamber 104, thereby enhancing the heating effect during the compression stroke and meeting the temperature requirements for ammonia fuel ignition.

[0046] The boost ratio is set to a high range to increase the intake pressure and intake volume through the turbocharger. At the same time, no intercooler is installed to retain the intake heat and further increase the cylinder temperature.

[0047] The ignition energy is set to a high energy range, which is achieved by optimizing the structure of spark plug 106 and the power supply system, ensuring that spark plug 106 can generate a spark with sufficient energy, breaking through the limitation of high minimum ignition energy of ammonia fuel.

[0048] The air-fuel equivalence ratio is set to cover a range from lean combustion to stoichiometric combustion, adapting to different operating conditions and balancing combustion efficiency and emission control. All parameters are coordinated and regulated by the control unit 110 to ensure that each parameter is matched and coordinated.

[0049] The combination of high compression ratio and boost ratio significantly increases the in-cylinder temperature and pressure at the end of compression, effectively solving the core problem of difficult ammonia ignition and laying the foundation for stable ignition of ammonia fuel. High-energy ignition parameters ensure sufficient spark energy to ignite the ammonia mixture, improving ignition success rate and stability, especially suitable for lean combustion conditions. A wide range of air-fuel equivalence ratios allows the engine to flexibly adjust under different load conditions, using lean combustion to improve efficiency at low loads and equivalence combustion to ensure power output at high loads, while reducing unburned ammonia and nitrogen oxide emissions. The synergistic optimization of various parameters enables the pure ammonia internal combustion engine to achieve efficient, stable, and low-emission operation without relying on other fuels, fully leveraging the zero-carbon advantages of ammonia fuel.

[0050] like Figure 13 As shown, the intake system of the pure ammonia internal combustion engine adopts a turbocharged but non-intercooled structural design. The core includes a turbocharger and its supporting pipelines, without the need for an additional intercooler. The combustion conditions in the cylinder are improved by retaining the heat of the intake air.

[0051] The turbocharger includes a turbine and a compressor. The turbine is connected to the engine exhaust side 134 via piping, and the compressor is connected to the engine intake side via piping. The two are rigidly connected by a turbine shaft 124, forming a power transmission structure. The turbine's intake inlet is connected to the engine exhaust side 134, and the turbine exhaust outlet 128 leads to the external exhaust system. The compressor's intake inlet 130 is connected to the air filter, and its exhaust outlet is connected to the engine cylinder 100 via an intake manifold 116. The entire intake and exhaust piping is wrapped with heat-insulating material to reduce heat loss.

[0052] When the engine is running, the high-temperature exhaust gas discharged from the exhaust side enters the turbine, driving the turbine impeller 126 to rotate, which in turn drives the compressor impeller 132 to rotate synchronously via the turbine shaft 124. As the compressor impeller 132 rotates, it draws in fresh outside air, compresses it, and increases the air pressure. Simultaneously, the air temperature naturally rises during compression. Because no intercooler is installed, the high-temperature, high-pressure compressed air directly enters the cylinder 100 through the intake manifold 116 without undergoing cooling, thus retaining the heat generated during compression and maintaining a high temperature for the air entering the combustion chamber 104.

[0053] During the turbocharging process, the air temperature rises naturally without being cooled by an intercooler. The high-temperature air directly enters the cylinder 100. Combined with the high compression ratio and thermal barrier coating, the cylinder temperature at the end of the compression stroke is significantly increased, which compensates for the high auto-ignition temperature of ammonia fuel. This provides sufficient heat for the stable ignition of ammonia fuel, avoids ignition failure in low-temperature environments, and improves the engine's starting and low-load operating stability.

[0054] According to one embodiment of the present invention, a fuel supply system is also included, the fuel supply system including an ammonia injector 112, the fuel supply system supplying ammonia fuel to the combustion chamber 104 through at least one of the following: supplying ammonia gas via the ammonia injector 112 using a continuous flow valve 114 and a plasma generator 120, supplying ammonia gas via an intake manifold 116, and supplying liquid ammonia via direct injection into the cylinder.

[0055] In one embodiment of the present invention, the fuel supply system is based on an ammonia injector 112 and provides three optional ammonia fuel supply methods, which can be flexibly selected or combined according to the engine operating conditions.

[0056] The first method involves supplying ammonia gas via a continuous flow valve 114: the ammonia fuel tank stores liquid ammonia, which enters the vaporizer through the ammonia pipeline and the ammonia check valve. After the liquid ammonia is vaporized, it forms ammonia gas, which is stably output through the continuous flow valve 114. After being activated by the plasma generator 120, it is injected into the air intake duct 116, mixed with air, and then enters the combustion chamber 104.

[0057] The second method involves injecting ammonia into the intake duct 116: after being pressurized by the ammonia check valve and the liquid ammonia pump, liquid ammonia is directly injected into the intake duct 116 through the ammonia injector 112. The ammonia and air are mixed in the intake duct 116 to form a premixed gas, which enters the combustion chamber 104 with the intake stroke.

[0058] The third method is direct injection of liquid ammonia into the cylinder: the ammonia injector 112 is installed on the cylinder 100 cover and aligned with the combustion chamber 104. After the liquid ammonia is pressurized to high pressure by the liquid ammonia pump, it is directly injected into the combustion chamber 104 through the ammonia injector 112 to achieve in-cylinder atomization and combustion of liquid ammonia.

[0059] All three types of ammonia injectors 112 are electrically connected to the control unit 110, which controls the injection timing and injection volume according to the operating conditions.

[0060] The flexible selection of three supply methods adapts to different engine operating conditions. The continuous flow valve 114 supply, combined with plasma activation, enhances ammonia reactivity, facilitating lean combustion. The intake manifold 116 injection supply technology is mature and suitable for stable operating conditions. In-cylinder direct injection of liquid ammonia allows for precise control of injection parameters, suitable for high-load conditions. These diverse supply methods overcome the limitations of a single supply method, optimizing fuel form and mixing for the combustion characteristics of ammonia fuel, promoting complete combustion and improving combustion efficiency. No additional fuel storage or reforming equipment is required; multiple supply modes are achieved through a single ammonia fuel tank, simplifying the system structure, reducing costs, and minimizing unburned ammonia emissions, ensuring zero-carbon combustion.

[0061] According to one embodiment of the present invention, it further includes an exhaust gas recirculation line 118 for recirculating hot exhaust gas from the exhaust side of the engine to the intake side; the ammonia injector 112 is configured to inject liquid ammonia into the hot exhaust gas in the exhaust gas recirculation line 118.

[0062] In one embodiment of the present invention, the pure ammonia internal combustion engine is equipped with an exhaust gas recirculation pipeline 118, an exhaust gas recirculation device 122, and a dedicated ammonia injector 112. One end of the exhaust gas recirculation pipeline 118 is connected to the engine exhaust side 134, and the other end is connected to the intake side, forming a circulation channel for hot exhaust gas. No cooling device is installed in the pipeline to ensure that the exhaust gas maintains a high temperature. The ammonia injector 112 is installed in the exhaust gas recirculation device 122 and located near the intake side connection end of the exhaust gas recirculation pipeline 118. Its injection port faces the hot exhaust gas flow inside the pipeline. The ammonia injector 112 is connected to the liquid ammonia pump and the ammonia fuel tank through an ammonia pipeline, allowing high-pressure liquid ammonia to be directly injected into the hot exhaust gas. The control unit 110 is electrically connected to the control valves of the ammonia injector 112 and the exhaust gas recirculation pipeline 118. It adjusts the liquid ammonia injection quantity and exhaust gas recirculation quantity according to the engine operating conditions, so that the liquid ammonia is rapidly atomized and evaporated in the hot exhaust gas to form a homogeneous ammonia-exhaust gas mixture, which then enters the combustion chamber 104 with the intake air to participate in combustion.

[0063] The high-temperature environment of the exhaust gas provides ample heat for the liquid ammonia, promoting its rapid atomization and evaporation, thus solving the problem of slow vaporization. Simultaneously, the ammonia is thoroughly mixed with the exhaust gas, improving the uniformity of the mixture. The introduction of exhaust gas recirculation lowers the combustion temperature, suppressing nitrogen oxide (NOx) formation, particularly mitigating high NOx emissions caused by low-temperature reaction pathways under low-load conditions. Premixing the liquid ammonia with the exhaust gas enhances combustion stability, increases the flame propagation speed of the ammonia fuel, and reduces unburned ammonia emissions. Through the synergy of exhaust gas recirculation and ammonia injection, the overall structure further optimizes the combustion performance of pure ammonia without relying on other fuels, improving the engine's environmental friendliness and reliability.

[0064] According to one embodiment of the present invention, the inner surface of the combustion chamber 104 is coated with a thermal barrier coating.

[0065] In one embodiment of the present invention, the inner surface of the combustion chamber 104, including the area of ​​the inner wall of the cylinder 100 corresponding to the combustion chamber 104, the top of the piston 102, and the bottom of the cylinder 100 cover corresponding to the combustion chamber 104, is uniformly coated with a thermal barrier coating. The thermal barrier coating is made of a material with high temperature resistance and excellent heat insulation performance. The coating thickness is uniform, the surface is smooth, and it does not affect the sealing performance of the combustion chamber 104 or the reciprocating motion of the piston 102. The coating covers the entire inner surface of the combustion chamber 104 without any omissions or damage, and can effectively prevent the heat in the combustion chamber 104 from being transferred to the cylinder 100 wall, piston 102, and other components, maintaining a high-temperature environment inside the combustion chamber 104.

[0066] The thermal barrier coating reduces heat loss through the combustion walls, increases the cylinder temperature at the end of the compression stroke, compensates for the high auto-ignition temperature of ammonia, and provides favorable temperature conditions for ammonia fuel ignition, thus improving the ignition success rate. The high-temperature environment promotes the oxidation reaction of ammonia, accelerates flame propagation, and ensures more complete combustion, reducing unburned ammonia emissions. Simultaneously, the coating protects the combustion chamber components from high-temperature corrosion, extending component lifespan and improving engine durability. By increasing cylinder temperature and reducing heat loss, the combustion efficiency of pure ammonia is further optimized, enabling stable engine operation under various conditions and enhancing the practicality of the pure ammonia internal combustion engine.

[0067] According to one embodiment of the present invention, it further includes an ammonia injector, the central axis of which forms a predetermined angle with the central axis of the glow plug 108 or the central axis of the spark plug 106.

[0068] In one embodiment of the present invention, an ammonia injector is installed on the cylinder 100 cap and arranged together with a glow plug 108 and a spark plug 106 in the top region of the combustion chamber 104. The central axis of the ammonia injector forms a predetermined angle with the central axis of either the glow plug 108 or the spark plug 106. This angle is optimized based on the shape of the combustion chamber 104, the nozzle position, and the installation position of the ignition device to ensure that the ammonia fuel spray from the injector accurately covers the ignition area. The layout of the ammonia injector, glow plug 108, and spark plug 106 has been optimized through simulation to ensure that the distance between the spray and the ignition source is appropriate, guaranteeing both sufficient atomization and mixing of the spray and effective contact between the ignition source and the mixture to form a stable ignition core. The control unit 110 coordinates the injection timing and injection quantity of the ammonia injector according to different ignition modes, working in conjunction with the angled layout to achieve optimal mixture formation and ignition effect.

[0069] The pre-defined angled layout design allows the ammonia fuel spray to be precisely guided near the ignition source, promoting the accumulation of the air-fuel mixture in the ignition zone, increasing the contact probability between the ignition source and the mixture, solving the problem of the narrow combustible range of ammonia fuel, and significantly improving the ignition success rate. The optimized distance between the spray and the ignition source avoids ignition failure caused by an overly rich spray or combustion instability caused by an overly lean spray, promoting rapid flame propagation and improving combustion uniformity. The coordinated control of the angled layout and injection parameters enables the engine to form an appropriate air-fuel mixture distribution under different ignition modes, enhancing combustion stability, reducing unburned ammonia emissions, and improving engine power output and fuel economy.

[0070] According to one embodiment of the present invention, the ammonia injector is configured to form a locally rich mixture region around the glow plug 108 by controlling at least one of the ammonia injection timing, the injection orifice position, and the injection angle. And / or, The ammonia injector is configured to inject ammonia fuel onto the high-temperature surface of the glow plug 108.

[0071] In one embodiment of the present invention, the ammonia injector optimizes ignition and combustion by precisely controlling key parameters.

[0072] The first configuration: The ammonia injector adjusts the injection timing, nozzle position, and injection angle to create a locally rich mixture around the glow plug 108. The nozzle is positioned towards the glow plug 108, the injection angle is precisely controlled, and the injection timing is selected at the beginning of the compression stroke to ensure that the spray gathers near the glow plug 108, forming a rich mixture.

[0073] The second configuration: The nozzle of the ammonia injector is directly aimed at the high-temperature surface of the glow plug 108, directly injecting liquid ammonia fuel onto the high-temperature surface. The high temperature of the glow plug 108 is used to achieve rapid atomization, evaporation, and cracking of the ammonia fuel to produce hydrogen. The two configurations can be used alone or in combination, and the control unit 110 can flexibly switch them according to the engine operating conditions.

[0074] The formation of locally rich mixture zones promotes the enrichment and hydrogen production reaction of ammonia fuel. The high reactivity of hydrogen reduces the ignition difficulty of ammonia and improves ignition stability, making it particularly suitable for engine start-up and low-load conditions. Directly injecting ammonia fuel onto the high-temperature surface of the glow plug 108 allows for rapid atomization and evaporation at high temperatures, shortening the mixture formation time and promoting ammonia cracking, further enhancing fuel reactivity and resulting in faster ignition and more complete combustion. The flexible switching between the two configurations adapts to different operating conditions, effectively solving the problems of difficult ammonia fuel ignition and slow flame propagation, reducing unburned ammonia emissions, improving engine operational stability and efficiency, and maintaining the zero-carbon advantage of pure ammonia combustion without relying on other fuels.

[0075] like Figure 14 As shown, a second aspect of the present invention provides a control method for a pure ammonia internal combustion engine as described above, comprising: Step 10, the first injection step, during the intake stroke, a first portion of ammonia fuel is injected into the combustion chamber 104 to form a homogeneous mixture; Step 20, the second injection step, during the compression stroke, injects a second portion of ammonia fuel into the combustion chamber 104 to form a stratified mixture; Step 30, ignition step, using at least one of spark plug 106 ignition, glow plug 108 ignition, and jet ignition.

[0076] According to the control method for a pure ammonia internal combustion engine provided in the second aspect of the present invention, the homogeneous mixture formed during the intake stroke ensures that the ammonia fuel and air are evenly distributed within the combustion chamber 104, avoiding incomplete combustion due to excessively rich mixtures or ignition failure due to excessively lean mixtures, thus providing a uniform basis for the subsequent formation of stratified mixtures. The formation of the homogeneous mixture relies on the intake airflow and the structure of the combustion chamber 104, eliminating the need for additional stirring components, simplifying the control logic, and simultaneously creating conditions for lean combustion of ammonia fuel, improving engine economy and reducing initial unburned ammonia residue. The stratified mixture formed during the compression stroke solves the problem of difficult ammonia fuel ignition through local concentration optimization. The higher concentration of the mixture at the center of the combustion chamber 104 is more easily ignited by an ignition source, while the peripheral homogeneous mixture ensures complete combustion, breaking the limitation of the narrow combustible range of ammonia fuel. The stratified structure also slows down the rate of temperature rise in the initial stage of combustion, inhibiting the formation of nitrogen oxides, especially improving the high nitrogen oxide emissions caused by the low-temperature reaction path of ammonia fuel under low-load conditions, balancing ignition stability and environmental friendliness. The control unit 110 selectively controls the spark plug 106 and / or glow plug 108 according to operating conditions to achieve stable ignition under all operating conditions: during startup, the high-temperature surface of the glow plug 108 compensates for the insufficient ignition energy of ammonia fuel in low-temperature environments; during stable operation, the spark plug 106 works alone to reduce energy consumption; under special operating conditions, the two work together to improve ignition reliability, without relying on the mixing of other highly reactive fuels, and stable ignition can be achieved with only pure ammonia, maintaining the advantage of zero-carbon combustion. The matching of ignition timing with stratified mixture further promotes rapid flame propagation, reduces unburned ammonia emissions, improves combustion efficiency, and ensures that the engine can operate efficiently and stably under different operating conditions.

[0077] Please continue reading Figure 14 The control method for a pure ammonia internal combustion engine provided in the second aspect embodiment of the present invention is mainly implemented through the following steps: Step 10, First Spray Step: During the engine intake stroke, after receiving the intake stroke trigger signal, the control unit 110 sends an injection command to the ammonia injector 112. The ammonia injector 112 is connected to the ammonia fuel tank and liquid ammonia pump through an ammonia pipeline. Upon receiving the command, the ammonia injector 112 injects the first portion of ammonia fuel according to the preset injection amount, and the ammonia fuel is directly injected into the combustion chamber 104. At this time, the combustion chamber 104 is in the intake state, and fresh air enters the combustion chamber 104 with the opening of the intake valve. The first portion of ammonia fuel injected into the combustion chamber 104 is fully mixed with the fresh air. With the help of the disturbance of the intake airflow and the spatial structure of the combustion chamber 104, a homogeneous mixture with uniform composition and concentration is formed, laying a uniform mixing foundation for subsequent combustion.

[0078] Step 20, Second Injection Step: After entering the engine compression stroke, the control unit 110 sends a second injection command to the ammonia injector 112 according to the progress of the compression stroke. The ammonia injector 112 injects a second portion of ammonia fuel according to the adjusted injection quantity, and the second portion of ammonia fuel is injected into the combustion chamber 104, which has formed a homogeneous mixture. As the piston 102 moves upward during the compression stroke, the space of the combustion chamber 104 gradually shrinks. The injected second portion of ammonia fuel forms a stratified mixture with local concentration differences on the basis of the homogeneous mixture. The concentration of the mixture in the central area of ​​the combustion chamber 104 is slightly higher, while the concentration of the mixture in the surrounding area remains homogeneous. This stratified structure is adapted to the narrow combustible range of ammonia fuel, providing a better mixture concentration environment for ignition.

[0079] In addition, it should be noted that the second injection step also has the effect of heat absorption, which can reduce heat transfer loss and reduce nitrogen oxide emissions.

[0080] Step 30, Ignition Step: The control unit 110 sends ignition commands to the spark plug 106 and glow plug 108 of the compound ignition system, or uses at least one of the following methods, depending on the current operating conditions of the engine (e.g., starting, low load, stable operation, high load). In the case of starting or low load conditions, the control unit 110 commands the glow plug 108 to energize and generate a high-temperature surface, triggering the ignition of ammonia fuel in the stratified mixture through high temperature. In the case of stable operation conditions, the control unit 110 commands the spark plug 106 to discharge alone, generating an ignition spark to ignite the stratified mixture. In the case of high load or special conditions, the control unit 110 commands the spark plug 106 to discharge in conjunction with the high temperature of the glow plug 108 to ensure stable ignition of the stratified mixture. If jet ignition is used, after the mixture in the pre-combustion chamber burns, a high-temperature, high-pressure jet is formed through a small orifice, igniting the mixture in the main combustion chamber. The ignition timing is matched with the end of the second injection step to ensure optimal contact between the ignition source and the stratified mixture, promoting rapid flame propagation.

[0081] According to one embodiment of the invention, the first injection step is performed within a crankshaft angle range of 330 degrees to 210 degrees before the top dead center of the compression, and the air-fuel equivalence ratio of the homogeneous mixture is 0.4 to 0.8.

[0082] In one embodiment of the invention, the first injection step of the control method is performed within a specific crankshaft angle range, which covers the main stage of the intake stroke, ensuring that the first portion of ammonia fuel has sufficient time to mix with air. The injection process is precisely controlled by the control unit 110 to regulate the opening duration and injection pressure of the ammonia injector 112, ensuring thorough mixing of the injected ammonia fuel with the air entering the combustion chamber 104, forming a homogeneous mixture with a fuel-air equivalence ratio within a specific range. This equivalence ratio falls within the lean combustion range of ammonia fuel, balancing combustion efficiency and emission control. The crankshaft angle range and fuel-air equivalence ratio parameters of the first injection step are optimized through engine bench testing to suit the combustion characteristics of ammonia fuel, synergizing with the parameters of the second injection step.

[0083] The selection of a specific crankshaft angle range provides sufficient time for homogeneous mixture formation, ensuring mixture uniformity and avoiding combustion instability caused by localized mixture concentration deviations. Setting the air-fuel equivalence ratio in the lean range improves engine economy while reducing NOx emissions, adapting to the combustible range characteristics of ammonia fuel. The parameters of the first injection step work in conjunction with the second injection step to lay the foundation for stratified combustion, making subsequent ignition more stable and flame propagation faster, further reducing unburned ammonia emissions. Through precise injection timing and equivalence ratio control, efficient combustion of pure ammonia fuel is achieved without relying on other fuels, improving the overall performance of the engine.

[0084] According to one embodiment of the invention, the second injection step is performed within a crankshaft angle range of 60 degrees to 0 degrees before the top dead center of the compression stroke, and after the second injection step, the equivalence ratio around the spark plug 106 is 1.0 to 1.2, and the overall equivalence ratio is 0.4 to 1.0.

[0085] In one embodiment of the invention, the second injection step of the control method is executed within a specific crankshaft angle range before the top dead center of the compression stroke. This range is close to the ignition point, ensuring that the second portion of ammonia fuel can quickly fuse with the homogeneous mixture after injection, forming a stratified structure. The control unit 110 precisely adjusts the injection amount of the second portion of ammonia fuel according to the injection amount of the first injection step, ensuring that the overall fuel-air equivalence ratio corresponding to the total injection amount of the two injections is within a specific range. This range covers the efficient combustion range of ammonia fuel, balancing power output and emission control. The injection pressure of the second injection step is higher than that of the first injection step, ensuring atomization and promoting rapid mixing with the homogeneous mixture while preventing the spray from hitting the walls.

[0086] The precise timing of injection before top dead center of compression allows the second portion of ammonia fuel to quickly form a stratified mixture before ignition. The higher concentration of the mixture in the central region of combustion chamber 104 improves the ignition success rate, while the surrounding homogeneous mixture ensures complete combustion, effectively solving the problem of slow flame propagation in ammonia. Precise control of the overall air-fuel equivalence ratio balances engine power output and emissions, ensuring sufficient power performance while reducing unburned ammonia and nitrogen oxide emissions. Higher injection pressure improves atomization quality, avoiding carbon buildup and increased emissions caused by fuel hitting the combustion chamber walls, further optimizing the combustion process. The coordinated control of the two injection parameters enables the pure ammonia internal combustion engine to achieve stable, efficient, and low-emission operation across the entire load range, fully leveraging the advantages of zero-carbon fuel.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pure ammonia internal combustion engine characterized by, The pure ammonia internal combustion engine comprises: a cylinder (100); a piston (102) configured to reciprocate within the cylinder (100); a combustion chamber (104) defined by the cylinder (100) and the piston (102), the combustion chamber (104) being a squish ported ball combustion chamber (104); a composite ignition system comprising a spark plug (106), a glow plug (108), and a control unit (110) configured to adopt at least one of spark ignition, glow plug ignition, and jet ignition based on an operating condition of the engine.

2. The pure ammonia internal combustion engine according to claim 1, characterized by The compression ratio of the pure ammonia internal combustion engine ranges from 20 to 25, the supercharging ratio ranges from 2 to 4, the ignition energy ranges from 100 to 300 mJ, and the overall fuel-air equivalence ratio ranges from 0.4 to 1.

0.

3. The pure ammonia internal combustion engine according to claim 1, characterized by The pure ammonia internal combustion engine further comprises a fuel supply system comprising an ammonia injector (112), the fuel supply system being configured to supply ammonia fuel to the combustion chamber (104) by at least one of a continuous flow valve (114) and a plasma generator (120) supplying ammonia gas, an intake port (116) injecting ammonia gas, and an in-cylinder direct injection injecting liquid ammonia.

4. The pure ammonia internal combustion engine according to claim 1, characterized by The pure ammonia internal combustion engine further comprises an exhaust gas recirculation line (118) for recirculating hot exhaust gas from an exhaust side of the engine to an intake side, and the ammonia injector (112) is configured to inject liquid ammonia into the hot exhaust gas in the exhaust gas recirculation line (118).

5. The pure ammonia internal combustion engine according to any one of claims 1 to 4, characterized by, An inner surface of the combustion chamber (104) is coated with a thermal barrier coating.

6. The pure ammonia internal combustion engine according to any one of claims 1 to 4, characterized by The pure ammonia internal combustion engine further comprises an ammonia injector (112) having a central axis forming a predetermined angle with a central axis of the glow plug (108) or a central axis of the spark plug (106).

7. The pure ammonia internal combustion engine according to claim 6, characterized by The ammonia injector (112) is configured to form a locally over-rich mixture region around the glow plug (108) by controlling at least one of an ammonia injection timing, an injection hole position, and an injection angle. The ammonia injector (112) is configured to inject ammonia fuel to a high-temperature surface of the glow plug (108). The pure ammonia internal combustion engine comprises:

8. A control method of a pure ammonia internal combustion engine as set forth in any one of claims 1 to 7, characterized by, a first injection step of injecting a first portion of ammonia fuel into the combustion chamber (104) during an intake stroke to form a homogeneous mixture; a second injection step of injecting a second portion of ammonia fuel into the combustion chamber (104) during a compression stroke to form a stratified mixture; an ignition step of adopting at least one of spark ignition, glow plug ignition, and jet ignition. The first injection step is performed in a range of 330 degrees to 210 degrees of a crank angle before a compression top dead center, and the homogeneous mixture has a fuel-air equivalence ratio ranging from 0.4 to 0.

8.

9. The control method according to claim 8, characterized by, The second injection step is performed in a range of 60 degrees to 0 degrees of a crank angle before a compression top dead center, and after the second injection step, an equivalence ratio combustion having an equivalence ratio ranging from 1.0 to 1.2 is performed around the spark plug (106), and an overall equivalence ratio ranges from 0.4 to 1.

0.

10. The control method according to claim 8, characterized by ​

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